//#include <windows.h>
#include <iostream>
#include <math.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

// use a named constant to approximate pi
const float pi = 3.14159265358979;

//--------------- setWindow ---------------------
// define our own function to specify the window, as explained later
void setWindow(GLfloat left, GLfloat right, GLfloat bottom, GLfloat top)

{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(left, right, bottom, top);
}


//---------------- setViewport ------------------
void setViewport(int left, int right, int bottom, int top)
// define our own function to specify the viewport, as explained later
{
    glViewport(left, bottom, right - left, top - bottom);
}

//<<<<<<<<<<<<<< myDisplay >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

void myDisplay(void) // plot the sinc function, using world coordinates

{
    glClear( GL_COLOR_BUFFER_BIT );
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glBegin(GL_LINE_STRIP);
/* automatically uses the defined window and viewport, 
clips properly, and performs the proper mapping */

        for(GLfloat x = -4.0; x < 4.0; x += 0.1)     // draw the plot
            glVertex2f(x, sin(pi * x) / (pi * x));

    glEnd();
    glFlush();
}

 

//<<<<<<<<<<<<<< myInit >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
void myInit(void)
{
    glClearColor(1.0,1.0,1.0,0.0);
    glColor3f(0.0f,0.0f,1.0f);
    glLineWidth(1.0);
}

//<<<<<<<<<<<<<<main>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(640,480);
    glutInitWindowPosition(100,150);
    glutCreateWindow("Sinc Function");
    glutDisplayFunc(myDisplay);
    myInit( );
    // call the function to specify the window
    setWindow(-5.0, 5.0, -0.3, 1.0);
    // call the function to specify the viewport
    setViewport(0, 640, 0, 480);
    glutMainLoop( );
}
